laser-driven relativistic optics and particle acceleration ... · laser-driven relativistic optics...
TRANSCRIPT
Laser-driven relativistic optics and
particle acceleration in ultrathin foils
Prof. Paul McKenna
University of Strathclyde, Glasgow, UK
[email protected]; GSI-22/05/2018
University of Strathclyde, Glasgow
• Founded in 1796 by John Anderson, Professor of Natural Philosophy as ‘a place of useful learning’
• Focus on Science and Engineering
• Became the University of Strathclyde in 1964
• 22,000 students and more than 3,000 staff
[email protected]; GSI-22/05/2018
Talk outline
1. Introduction to high power lasers – SCAPA facility
2. Concepts in relativistic laser-plasma physics
3. Overview of our results using PHELIX (since 2010)
4. Laser-driven ion acceleration overview
5. Relativistic plasma aperture formation and laser diffraction
6. Enhancing ion energy via hybrid acceleration schemes
[email protected]; GSI-22/05/2018
Achievable laser intensity…
1.E+10
1.E+12
1.E+14
1.E+16
1.E+18
1.E+20
1.E+22
1.E+24
1960 1970 1980 1990 2000 2010 2020
Year
La
se
r in
ten
sity (
W/c
m^2
)
Strong-field QED plasma
Relativistic plasma
Plasma
1024
1022
1020
1018
1016
1014
1012
1010
Ach
ieva
ble
lase
r in
ten
sity
(W
/cm
2)
E >> mec2
E > mec2
4
Chirped pulse amplification (CPA)
Oscillator
Stretcher
Amplifier
Compressor
Extreme Light Infrastructure (ELI)
Central Laser Facility, RAL Phelix, GSI
[email protected]; GSI-22/05/2018
SCAPA: Scottish Centre for
Applications of Plasma Accelerators
• 3 shielded areas with multiple beam lines.
• High-intensity fs laser systems:
a) 350 TW at 5 Hz,
b) 40 TW at 10 Hz,
c) sub-TW at kHz.
• High-energy ion and electron bunches,
• Bbright X-ray/g-ray and neutron pulses.
Level 2
Level 1
[email protected]; GSI-22/05/2018
SCAPA 350 TW laser commissioned
[email protected]; GSI-22/05/2018
Collective electron dynamics in laser-plasma
High power laser pulse
Uniform plasma
Electrons
8
[email protected]; GSI-22/05/2018
Collective electron dynamics in laser-plasma
High power laser pulse
Uniform plasma
Electrons
9
In the interaction of a laser pulse with plasma, electrons collectively quiver around the (almost) stationary ions plasma oscillations
Electron plasma frequency:
Electron density
Electron mass
If plasma > (Laser) the plasma electrons can follow the light oscillations and therefore cancel the light propagation.e
e
m
ne
0
2
plasma
[email protected]; GSI-22/05/2018
Relativistic non-linear optics
Electron mass increase by the relativistic factor
• Refractive index
• phase velocity vph=c/n is smaller on-axis
• plasma acts like a positive lens - self-focusing for powers beyond critical level.
Relativistic Self-Focussing
• In dense plasma with ωp > ωLas, light cannot propagate
• The dispersion relation governing laser light propagation depends on plasma frequency ωp
2=4πe2ne/m and the average <g>-factor.
• Plasma becomes transparent for large <g>
Relativistic Induced Transparency
phase front
𝛾 =1
1 − ൗ𝑣2𝑐2
𝑛 = 1 −Τ𝜔𝑝
2 < 𝛾 >
𝜔𝐿𝑎𝑠2
[email protected]; GSI-22/05/2018
11
High power laser pulse
Uniform plasma
Electrons
Gas Solid
Underdense plasma
Wakefield bubble
e- laser
Wakefield electron acceleration
plasma < Laser
Collective electron dynamics in laser-plasma
[email protected]; GSI-22/05/2018
12
High power laser pulse
Uniform plasma
Electrons
Overdense plasma
Electron transport e.g. for Fast Ignition ICF
x
Gas Solid
plasma > Laser
Collective electron dynamics in laser-plasma
[email protected]; GSI-22/05/2018
13
Coury et al App. Phys. Lett., 100, 074105
(2012) & Brenner et al LPB (2012)
Laser focus effects
Dual-pulse optimisation
Scott et al App. Phys. Lett., (2012) Markey et al Phys. Rev Lett., 105, 195008 (2012)
0 5 10 15 200
5
10
15
20
25
30
35
40
45
ILP
(TW/cm2)
E max
(MeV
)
Al/Cu/CH
Cu[ref]
0 5 10 15 200
1
2
3
4
5
6
7
ILP
(TW/cm2)
lase
r->pr
oton
(%)
Al/Cu/CH
Cu[ref]
McKenna et al LPB, 12, 045018 (2010) Gray et al, New J. Physics (2014)
Optimum density gradients
Mass-limited targets
Tresca et al PPCF 53, 105008 (2011)Gray et al App. Phys. Lett, 99, 171502 (2011)
‘Shaping’ the ion beam
Tresca et al PPCF 53, 105008 (2011)
ions
Progress in intense laser-solid interactions
[email protected]; GSI-22/05/2018
Progress in intense laser-solid interactions
14
McKenna, et al., Phys. Rev. Lett. 98, 145001 (2007)Ge et al App. Phys. Lett, 107, 091111 (2015)
ions
Role of lattice structure in the resistivity of transient
Warm Dense Matter and electron transportTemperature map:Magnetic field:
MacLellan et al, Phys. Rev. Lett. 111, 095001 (2013)MacLellan et al, Phys. Rev. Lett., 113 185001 (2014)R. J. Dance, et al., Plas. Phys. Cont. Fus, 58, 014027 (2016)
ff jjB
t
McKenna et al , Phys. Rev. Lett. 106, 184004 (2011)
McKenna et al , Plas. Phys. Cont. Fus. 57, 064001(2015)
Vitreous carbon
Diamond
Manipulating fast electron transport via
self-generated resistive magnetic fields
Fast electron recirculation
Yuan et al, New J. Phys. 12, 063018 (2010)Quinn et al, PPCF, 53, 025007 (2011)Gray et al, New J. Phys. 20, 033021 (2018)
Lateral fast electron transport
[email protected]; GSI-22/05/2018
• Large volume Ulbricht sphere developed
• Used to investigate laser energy absorption as a function of laser and target properties
Total energy absorption studies using Phelix
Gray et al, New J. Phys. 20, 033021 (2018)
[email protected]; GSI-22/05/2018
Total energy absorption studies using Phelix
• Different scaling with intensity measured when focal spot is varied as opposed to pulse energy
• EPOCH PIC simulations and analytical modelling shows that absorption is enhanced when significant fast electron refluxing occurs within the target
Gray et al, New J. Phys. 20, 033021 (2018)
[email protected]; GSI-22/05/2018
Weibel instability in ion acceleration using Phelix
G. Scott et al, New Journal of Physics, 19, 043010 (2017)
• Double pulse configuration used
• Prepulse to main pulse energy ratio: 1:10
• Total laser energy on target: 72 ± 2 J
• Time between pulses: 1-100 ps
• Main pulse intensity: 4x1018 Wcm-2
Onset of Weibel instability in expanding dense plasma Investigated using a double laser pulse (pump-probe) scheme
[email protected]; GSI-22/05/2018
Spatial-intensity distribution of sheath-accelerated proton beam is modulated due to Weibel instability in preplasma at target foil rear surface
Fundamental plasma physics interest and imposes constraints on the preplasma levels tolerated for high quality proton acceleration
Weibel instability in ion acceleration using Phelix
G. Scott et al, New Journal of Physics, 19, 043010 (2017)
Weibel instability growth with increase plasma expansion (increasing temporal separation)
[email protected]; GSI-22/05/2018
Strathclyde publications from Phelix experiments 2011-18
1. Escaping electrons from intense laser-solid interactions as a function of laser spot size, Rusby et al., Euro. Phys. Journal 167, 02001 (2018)
2. Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents, Gray et
al., New J. Phys. 13 (2018)
3. Diagnosis of Weibel instability evolution in the rear surface scale lengths of laser solid interactions via proton acceleration, Scott, et al., New J. Phys. 19, 043010 (2017)
4. Role of lattice structure and low temperature resistivity on fast electron beam filamentation in carbon, Dance et al., Plasma Phys. Control. Fusion. 58, 014027, (2015)
5. Measurement of the angle, temperature and flux of fast electrons emitted from intense laser-solid interactions, Rusby et al., J. Plasma Phys. 81, 5, 9 p., 475810505, (2015)
6. Directed fast electron beams in ultraintense picosecond laser irradiated solid targets, Ge et al., Appl. Phys. Lett.. 107, 9, 5 p., 091111, (2015)
7. Optimisation of plasma mirror reflectivity and optical quality using double laser pulses, Scott et al., New J. Phys. 16 (2015)
8. The influence of preformed plasma on the surface-guided lateral transport of energetic electrons in ultraintense short laser-foil interactions, Yuan et al., Plasma Phys. Cont. Fus. 56, 055001, (2014)
9. Multi-pulse enhanced laser ion acceleration using plasma half cavity targets, Scott et al., Appl. Phys. Lett., 101, 024101 (2012)
10. Surface Transport of Energetic Electrons in Intense Picosecond Laser-Foil Interactions, Gray et al., Appl. Phys. Lett., 99, 171502 (2011)
11. Spatially resolved X-ray spectroscopy using a flat HOPG crystal, Yuan et al., Nucl. Instrum. Methods A, 653 (1). pp. 145-149 (2011)
12. Controlling the properties of ultraintense laser–proton sources using transverse refluxing of hot electrons in shaped mass-limited targets, Tresca et al., Plasma Phys. Cont. Fus. 53, 105008 (2011)
13. Refluxing of fast electrons in solid targets irradiated by intense, picosecond laser pulses, Quinn et al., Plasma Phys. Cont. Fus. 53, 025007 (2011)
20
High power laser pulse
Uniform plasma
Electrons
Overdense plasma
Electron transport e.g. for Fast Ignition ICF
x
Underdense plasma
Wakefield bubble
e- laser
Wakefield electron acceleration
Gas Solid
plasma > Laserplasma < Laser
Collective electron dynamics in laser-plasma
[email protected]; GSI-22/05/2018
21
High power laser pulse
Uniform plasma
Electrons
Overdense plasma
x
Foils expanding to near critical density plasma
Underdense plasma
Wakefield bubble
e- laser
Wakefield electron acceleration
Gas Solid
plasma > Laserplasma < Laser plasma ~ Laser
Electron transport e.g. for Fast Ignition ICFIon acceleration and HHG
Collective electron dynamics in laser-plasma
[email protected]; GSI-22/05/2018
Laser-ion acceleration mechanisms
p<Las
p>Las
p=Las
Numerous acceleration mechanisms have been identified, in overdense, underdense and near critical density targets
[email protected]; GSI-22/05/2018
Ion acceleration
0
General features of Target Normal Sheath Acceleration
Plasma expansion dynamics
Broad energy spectrum of ions
Divergence decreases with increasing ion energy
Sheath field established on foil surface
[email protected]; GSI-22/05/2018
Laser-ion acceleration mechanisms
p<Las
p>Las
p=Las
At high enough intensity, radiation pressure drives plasma surface inwards: Hole Boring
uHB
[email protected]; GSI-22/05/2018
Laser radiation pressure accelerationRadiation pressure via Photons
Photon flux (no. of photons per sec per unit area; units cm-2s-1):
Momentum flux or Pressure (force per unit surface):
𝐹𝑝ℎ =𝐼𝐿ℏ𝜔𝐿
𝑃𝑟𝑎𝑑 = ℏ𝑘𝐹𝑝ℎ =𝐼𝐿𝑘
𝜔𝐿
The laser ponderomotive force pushes and piles up electrons in the skin layer creating a static field that acts on the ions.
Z (microns)
Ion density
Electron density
Electric field
Results in an ion population with energy per nucleon equal to:
𝜀𝐻𝐵 =𝑚𝑝
2(2𝑢𝐻𝐵)
2=2𝑚𝑝𝐼𝐿𝜌𝑐
= 2𝑚𝑒𝑐2𝑍𝑛𝑐𝐴𝑛𝑒
𝑎02
uHB
[email protected]; GSI-22/05/2018
T. Esirkepov, et al., PRL. 92, 175003 (2004)Predicted beam properties:
• Fast scaling with laser intensity
• Narrow-band spectrum (whole-foil acceleration)
• Narrow divergence (assuming large focal spot)
p<Las
p>Las
p=Las
Relativistic transparency
enhanced acceleration
Plasma frequency:
e
ep
m
ne
0
2
Transparency when p<L
[email protected]; Oxford-05/03/2018
3D PIC simulations with a uniform planar target foil
Temporal evolution of plasma aperture:
Deformation due to radiation pressure
produces relativistically induced transparency over a diameter of a few times the laser wavelength𝜔𝑝
𝛾
[email protected]; GSI-22/05/2018
3D PIC simulations with a uniform planar target foil
Temporal evolution of plasma aperture:
Ponderomotive expulsion
Deformation due to radiation pressure
Hertz vector
diffraction theory
for a fixed aperture [email protected]; GSI-22/05/2018
Influence of laser polarisation
Circular
Elliptical
angle of the
polarization vectorangular velocity
of vector rotation
Linear – fixed diffraction pattern
Circular – rotating pattern at constant velocity
Elliptical – variable velocity of rotation
[email protected]; GSI-22/05/2018
Gonzalez-Izquierdo et al, Nature Physics, 12, 505 (2016)
Influence of laser polarisation
Circular polarisation
Gonzalez-Izquierdo et al, Nature Physics, 12, 505 (2016)
[email protected]; GSI-22/05/2018
Comparison between experimental and
simulations results
Elliptical CircularLinear Linear
10nm Al 40nm Al
Experiment:
3D PIC
simulation:
[email protected]; GSI-22/05/2018
Gonzalez-Izquierdo et al, Nature Physics, 12, 505 (2016)
Influence on ion acceleration
Electron density structure mapped into the proton beam via modulation of the electrostatic field
Gonzalez-Izquierdo et al., Nature Communications 7, 12891 (2016)
[email protected]; GSI-22/05/2018
Electron distribution maps into the protons
via the electrostatic field
Electrons:
Protons:
Linear pol. Circular pol.
Experiment 3D PIC
simulationExperiment 3D PIC
simulation
[email protected]; GSI-22/05/2018
Gonzalez-Izquierdo et al., Nature Communications 7, 12891 (2016)
Nuclear activation measurements confirm proton energy >92 MeV63Cu(p,n)63Zn
38 min half-life
Stacked RCF dosimetry film measurements: 94<Ep<101 MeV
Measurements of proton acceleration
Plasma mirror used to enhance the intensity contrast
[email protected]; GSI-22/05/2018
High proton energies obtained on Vulcan
Optimisation as a function of foil thickness has resulted in >95 MeV protons (between 94 MeV and 101 MeV)
Higginson et al, Nature Communications, 9, 724 (2018)
[email protected]; GSI-22/05/2018
High proton energies obtained on Vulcan
Optimisation as a function of foil thickness has resulted in >95 MeV protons (between 94 MeV and 101 MeV)
Higginson et al, Nature Communications, 9, 724 (2018)
[email protected]; GSI-22/05/2018
High proton energies obtained on Vulcan
Optimisation as a function of foil thickness has resulted in >95 MeV protons (between 94 MeV and 101 MeV)
Higginson et al, Nature Communications, 9, 724 (2018)
Correlated to measurements
of critical surface velocity
and transparency
[email protected]; GSI-22/05/2018
Hybrid acceleration schemes
Linearly polarised laser results in a dual-peaked electrostatic field, produced by RPA and TNSA
RPA(R)
TNSA(S)
Higginson et al, Nature Communications, 9, 724 (2018)
Laser pulse profile
TNSA RPA Transparency
t
[email protected]; GSI-22/05/2018
Transparency-enhanced accelerationTransmission of part of the laser pulse can enhance the TNSA field, by further heating the electrons, resulting in RIT-enhanced acceleration
Electron density Electron energy Electrostatic field
High energy electron jet formedAzimuthal magnetic field
Powell et al, New J. Phys. 17, 103033 (2015)
Experiment:
[email protected]; GSI-22/05/2018
1.E+10
1.E+12
1.E+14
1.E+16
1.E+18
1.E+20
1.E+22
1.E+24
1960 1970 1980 1990 2000 2010 2020
Year
La
se
r in
ten
sity (
W/c
m^2
)
Strong-field QED plasma
Relativistic plasma
Plasma
1024
1022
1020
1018
1016
1014
1012
1010
Ach
ieva
ble
lase
r in
ten
sity
(W
/cm
2)
E >> mec2
E > mec2
41
Central Laser Facility, RAL
Extreme Light Infrastructure (ELI)
Phelix, GSI
[email protected]; GSI-22/05/2018
Scaling to multi-PW facilities: 1022 Wcm-2
[email protected]; GSI-22/05/2018
Linearly polarised laser light → Hybrid RPA-TNSA acceleration
Optimum for hybrid acc. L=800 fs
RSIT onset L=40 fs
Optimum for hybrid acc. L=40 fs
RSIT onset L=800 fs
RPA(R)
TNSA(S)
Laser pulse profile
TNSA RPA Transparency
time
E
Limits for RPA-dominated hybrid regime calculated using the model in B. Qiao et al., Phys. Rev. Lett. 108, 115002 (2012)
Scaling to multi-PW facilities: 1022 Wcm-2
Linearly polarised laser light → Hybrid RPA-TNSA acceleration
Optimum for hybrid acc. L=800 fs
RSIT onset L=40 fs
Optimum for hybrid acc. L=40 fs
RSIT onset L=800 fs
Tune thickness to get a spectral peak or enhance the maximum energy
IL=1022 Wcm-2; L=40 fs
[email protected]; GSI-22/05/2018
Limits for RPA-dominated hybrid regime calculated using the model in B. Qiao et al., Phys. Rev. Lett. 108, 115002 (2012)
Summary points regarding ultrathin foil interactions
1. High contrast, short pulse intense laser interaction with ultrathin
foil produces a relativistic plasma aperture, resulting in diffraction
2. The diffraction pattern and collective plasma response is strongly
influenced by the degree of ellipticity in the laser polarization
3. Collective electron response is mapped into the proton beam
spatial-intensity distribution
4. Near-100 MeV protons measured (with two diagnostics) using the
Vulcan PW laser
5. Linearly polarised laser pulses drive a hybrid RPA-TNSA dual
peaked electrostatic field acceleration scheme, enhanced by
relativistic transparency occurring near the pulse peak
6. Hybrid acceleration scheme is scalable to next generation multi-
PW lasers and offer new opportunities for ion beam control
[email protected]; GSI-22/05/2018
Thank you for your attention!
Acknowledgements:• The staff at the Central Laser Facility, RAL and PHELIX group at GSI• EPSRC and STFC research funding councils• Laserlab-Europe
45
References to ultrathin foil:
1. A. Higginson et al, Nature Communications, 9, 724 (2018)
2. B. Gonzalez-Izquierdo et al., Applied Sciences. 1-18, (2018)
3. B. Gonzalez-Izquierdo et al, Nature Physics, 12, 505 (2016)
4. B. Gonzalez-Izquierdo et al, Nature Communications, 7, 12891 (2016)
5. B. Gonzalez-Izquierdo et al, High Power Laser Sci. Eng., 4, 33 (2016)
6. H. Powell et al, New J. Phys. 17, 103033 (2015)
7. M. King et al, Nuc. Instrum. Meth. A, 829, 163 (2016)
8. H. Padda et al, Phys. Plasmas, 23, 063116 (2016)
[email protected]; GSI-22/05/2018